Radiofrequency arc



Feb. 23 1926. 1,574,472

H. F. ELLIOTT RADIOFREQUENGY ARC -F"iled June 22, 1921 WITNESS INVENTOR ATTORNEYS Patented Feb. 23, 1926.

UNITED STATES PATENT FFICE.

HAROLD F. ELLIOTT, OF PALO ALTO, CALIFORNIA, ,ASSZGNOB, BY MESNE ASSIGN- MENTS, TO FEDERAL TELEGRAPH COMPANY, OF SAN FRANCISCO, UALIFOBNIA, A

CORPORATION OF CALIFORNIA.

RADIOFREQUENCY ARC.

Application filed June 22, 1921.

T 0 all whom it may concern:

Be it known that I, HAROLD F. ELLIOTT, a citizen of the United States, and a resident of Palo Alto, county of Santa Clara, and State of California, have invented certain new and useful Improvements in Radiofrequency Arcs, of which the following is a specification.

The invention relates to arcs for producing radiofrequency oscillating current. In the operation of radiofrequency are converters, it has been found that the antenna current, other factors being equal, is a maximum for a certain arc gap length, and decreases when this length is varied in either direction. During operation there is a tendency for the arc gap length to vary, reducing the efficiency of the converter and it is an object of this invention to maintain the arc gap at the proper length for the production of optimum results.

Another object of the invention is to provide means for automatically maintaining the arc gap length constant.

The invention possesses other advantageous features, some of which with the foregoing, will be set forth at length in the following description Where I shall outline in full that form of the invention which I have selected for illustration in the drawings accompanying and forming part of the present specification. In said drawings I have shown one embodiment of my invention, but it is to be understood that I do not limit myself to such form, since the invention, as set forth in the claims, may be embodied in a plurality of forms.

Referring to said drawings:

Fig. 1 is a diagrammatic representation of an arc radio converter embodying my invention.

Fig. 2 is a detail showing one form of means for moving one electrode.

The invention relates to a system of maintaining the adjustment of the electrodes in an arc radio converter. Such converter usually comprises two electrodes between which an arc is formed, one of the electrodes being usually metallic and the other being ordinarily carbon, and during the operation of the converter, the length of the arc gap varies, due to wear on the carbon or to Serial No. 479,497.

other causes. It has been found desirable to maintain the arc gap at a predetermined length to produce the maximum antenna current and this is accomplished in the present invention by automatically adjusting one or both of the electrodes during the operation of the converter. In operating an arc converter it is found that the antenna current is a maximum for any given conditions of antenna resistance, supply voltage, wavelength, etc., when a certain gap length between the electrodes used. When the gap is shortened or lengtlencd from the optimum adjustment, the antenna current is reduce. The supply current also tends to follow the -enna current and is also less than maximum when the gap is either too long or too short, except when thegap becomes so short that a short circuit exists.

To maintain the are gap in adjustmen 1 have employed a eha teristic of the are which varies continuously with and follows are adjustment. Such a ciaracteristic is found in the voltage across the electrodes and in the voltage across certain other portions of the associated circuits, for instance across an inductance 2 in the antenna circuit 3; across the choke coil a in the supply c' cuit; between the loading inductor and earth and across the electrodes 6 and 7. In the drawings I have shown the control circuit connected across the electrod s, but it is to be understood that it may be connected across any other lenient in the system, wherein the voltage drop varies with the arc length. A contact making voltmeter 8, preferably of the hot wire type, is connected across the electrodes through a stopping condenser 9 and a multiplier 12. The voltmeter arm 13 carries a contact 14 which, when the arc is adjusted to the optimum length, lies intermediate the adjustable contacts 15 and 16. When the gap is decreased in length, the voltage across the are decreases and contact lei moves into engagement with contact 15 closing a circuit which causes the arc gap to be lengthened. Conversely, when the gap becoi 1e too long, cont ct l l moves into engagement with contact 16, closing a circuit which causes the arc gap to be shortened. A contact making ammeter may be used, instead of a vol meter, when desired,

but its functioning will be due to voltage variations in the circuits.

Connected to the arm 13 and the contacts 15 and 16 is a relay comprising the solenoids 17 and 18 and the switches 21 and 22 in the circuit of the reversible motor 23. The motor is mechanically connected in any suitable manner with one or both electrodes. so that rotation of the motor rotor in one direction causes the electrodes to be moved apart and in the other direction to be moved together. If the arc becomes too short, the voltmeter closes the relay circuit, which closes the motor circuit to cause the electrodes to be separated and vice versa. Instead of using the relay and motor, any suitable devices, such as hydraulic or pneu matic relays or motors, may be employed.

The voltage of the supply current should be maintained constant and any suitable or standard devices may be employed for that purpose.

In Fig. 2 I have shown one means which may be employed for moving an electrode 6 longitudinally to maintain the arc gap length. Secured to the electrode is an in sulating bushing 24 whichextends through the converter housing, and which is slidable but not rotatable in the housing. Secured to the bushing is a threaded sleeve 25 which is engaged by a threaded sprocket 26 which is driven'by the motor. The sprocket is held from longitudinal displacement by abutments 27 so that rotation of the sprocket produces longitudinal movement of the electrode. When both electrodes are adjustable, the threads are formed in opposite directions so that the electrodes move simultaneously in opposite directions. It is to be understood that the apparatus indi cated in the drawings is merely illustrative and that the invent-ion is in no manner limited to the apparatus shown.

I claim:

1. In a system for producing high frequency current oscillations with an are, a pair of electrodes between which the are is formed, a circuit connected to the electrodes, and means for adjusting the distance between the electrodes so as to produce an optimum value as regards the are output, comprising mechanism responsive only to variations beyond definite limits of the voltage drop across a part o1 the arc circuit for moving the electrodes relatively to each other.

2. In a system for producing high frequency current oscillations with an are, a pair of electrodes between which the arc is formed, a circuit connected to the electrodes and arranged to utilize the arc current, and means for adjusting the electrodes so as to produce an optimum value as regards the are output, comprising mechanism responsive only to variations beyond definite limits of an electrical characteristic of the circuit for moving the electrodes relatively to each other.

3. In a system for producing high frequency current oscillations with an are, a pair of electrodes between which the arc is formed, and means for adjusting the electrodes so as to produce an optimum value as regards the are output, comprising mechanism responsive to variations beyond delinite limits of the voltage drop across the electrodes for moving the electrodes relatively to each other.

In testimony whereof, I have hereunto sol my hand.

HAROLD F. ELLIOTT. 

